Belt tension measuring system and method

ABSTRACT

A method of checking belt tension of a belt extending between two or more pulleys includes providing a reference indicator defining a reference position relative to the upper surface of the belt in an undeflected state. A force/probe assembly is provided and has measurement markings. The distal end of the force/probe assembly is positioned on the upper surface of the belt at a midpoint of the span. A force is applied generally perpendicular to the upper surface of the belt using the force/probe assembly. The belt may be deflected a predetermined distance, as determined by using the measurement markings, and the force applied is measured, or a force is applied to the belt until the force is equal to a predetermined force, and the deflection of the belt is measured using the measurement markings. The belt tension is determined based on the force and distance during the deflecting step.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 63/001,089, filed Mar. 27, 2020, the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to systems and methods for measuring belttension in a system including a belt extending over two or more pulleys.

BACKGROUND OF THE INVENTION

Many mechanical systems utilize two or more pulleys with a beltextending over the pulleys to transmit power. It is important that thebelt be tensioned properly. Too little tension increases wear andreduces power transmission capacity and too much tension reduces beltlife and increase bearing wear. There are a wide variety of systems andmethods intended to assist in the measurement of belt tension, but theyare generally difficult or complicated to use, or provide inconsistentresults. As such, there is a need for additional systems and methods.

SUMMARY OF THE INVENTION

The present invention provides a system and method for measuring belttension in a system having a belt extending over two or more pulleys,with a span defined between the pulleys. In an embodiment, a referenceindicator is provided to define a reference position relative to anupper surface of the belt in an undeflected state. This referenceindicator may take various forms, with an exemplary version includingone or more laser alignment elements which project laser light in aplane. The light defines the reference position. In an example, thelaser alignment elements are attached to the pulleys and are positionedto project light at each other generally in the same plane. A probeelement has a distal end used to apply a force generally perpendicularlyto the upper surface of the belt at a midpoint of the span. The probeelement has measurement markings thereon and as the probe element isused to apply force to the belt, the position of these measurementmarkings moves relative to the reference position, thereby allowing auser to determine how much the belt has been displaced. The probeelement is connected to a force measurement device such that the forcemeasurement device measures the force being applied to the belt by theprobe element. Using the system, a force is applied to the upper surfaceof the belt either until the belt is displaced by a predetermined amountor until a predetermined force is applied. The belt tension may then bedetermined by comparing the displacement and force to the displacementand force that is specified for the belt or belt system.

A first embodiment of a method of checking belt tension includesproviding a reference indicator defining a reference position relativeto the upper surface of the belt in an undeflected state. A force/probeassembly is provided and is operable to measure a force. The assemblyhas measurement markings disposed thereon, and a distal end, and isconfigured to measure a force applied to the distal end. The distal endof the force/probe assembly is positioned on the upper surface of thebelt at a midpoint of the span and a force is applied generallyperpendicularly to the upper surface of the belt using the force/probeassembly. In one approach, the belt is deflected a predetermineddistance, as determined by a change in position of the measurementmarkings relative to the reference indicator, and the force appliedgenerally perpendicularly to the outer surface using the force/probeassembly is measured. In another approach, the belt is deflected usingthe force/probe assembly until the force applied generallyperpendicularly to the upper surface is equal to a predetermined force,and the deflection of the belt is measured, as determined by a change inposition of the measurement markings relative to the referenceindicator. The belt tension is determined based on the force anddistance during the deflecting step.

In an example, the force/probe assembly includes a force measurementdevice operable to measure a force and a probe element having themeasurement markings disposed thereon, the probe element having an enddefining the distal end of the force/probe assembly. The probe elementis connected with the force measurement device such that a force appliedto the end of the probe element is measured by the force measurementdevice.

A linear position of the measurement markings of the probe element maybe adjustable relative to the distal end of the force/probe assembly,and the method may further include, after the positioning step,adjusting the linear position of the measurement markings relative tothe distal end until the reference indicator is aligned with a zerolocation of the measurement markings.

The probe element may have a shaft and a measurement element movablyreceived on the shaft, the measurement element having the measurementmarkings disposed thereon. The zero location of the measurement markingsmay be an end of the measurement element.

The probe element may have an indicator movable relative to themeasurement markings, and the method may further include positioning theindicator at a predetermined position prior to the applying step, theposition corresponding to the predetermined deflection of the belt.

The probe element may be separable from the force measurement device andthe method may further include disposing the probe element on the forcemeasurement device such that a force applied to the end of the probeelement is measured by the force measurement device.

In some examples, the step of providing the reference indicator includesproviding a first laser alignment element operable to project laserlight in a plane and positioning the first laser alignment element suchthat the laser light in the plane is projected generally parallel to theupper surface of the belt in the undeflected state. The change inposition of the measurement markings relative to the reference indicatoris the change in position of the measurement markings relative to theprojected laser light. In some examples, a second laser alignmentelement is provided and is operable to project laser light in a plane.The second laser alignment element is positioned such that the laserlight projected by the second laser alignment element is generally inthe same plane as the laser light from the first laser alignmentelement.

The steps of positioning the first and second laser alignment elementsmay include attaching the alignment elements to respective ones of thetwo or more pulleys such that the alignment elements project lighttowards each other.

In some examples, a first and second support bracket are provided, andthe step of attaching the alignment elements to the respective pulleysincludes attaching a respective one of the support brackets to eachpulley and attaching each alignment element to the respective supportbracket. The first and second support brackets may be right-anglebrackets each having a first surface attachable to a face of a pulleyand a second surface at a right angle to the first surface, the secondsurface of each support bracket supporting a respective one of thealignment elements. The support brackets may each have magnets formagnetically attaching to the face of the respective pulley.

In some examples, the measurement markings of the force/probe assemblyinclude displacement markings and span markings corresponding to thedisplacement markings, the displacement marking associated with eachspan marking indicating a displacement to be used for the respectivespan indicated by the span marking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary system for practicing themethod according to an embodiment of the present invention;

FIG. 2 is a front view of the system of FIG. 1;

FIG. 3 is a perspective view of portions of an alignment element for usewith some embodiments of the present invention; and

FIG. 4 is perspective view of an embodiment of a force/probe assemblyfor use with some embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present system and method for measuring belt tension is for use witha system having a belt extending over two or more pulleys, with a spandefined between the pulleys. In an embodiment, a reference indicator isprovided to define a reference position relative to an upper surface ofthe belt in an undeflected state. This reference indicator may takevarious forms, with a preferred version including one or more laseralignment elements which project laser light in a plane. The lightdefines the reference position. In an example, the laser alignmentelements are attached to the pulleys and are positioned to project lightat each other generally in the same plane. A probe element has a distalend used to apply a force generally perpendicularly to the upper surfaceof the belt at a midpoint of the span. The probe element has measurementmarkings thereon and as the probe element is used to apply force to thebelt, the position of these measurement markings moves relative to thereference position, thereby allowing a user to determine how much thebelt has been displaced. The probe element is connected to a forcemeasurement device such that the force measurement device measures theforce being applied to the belt by the probe element. Using the system,a force is applied to the upper surface of the belt either until thebelt is displaced by a predetermined amount or until a predeterminedforce is applied. The belt tension may then be determined by comparingthe displacement and force to the displacement and force that isspecified for the belt or belt system.

Turning now to FIGS. 1 and 2, an exemplary system and method will bedescribed. A power transmission assembly 10 is represented by a firstpulley 12, a second pulley 14, and a belt 16 extending between thepulleys. The illustrated power transmission assembly 10 is a trainingdevice for training technicians to properly align and tension pulleysystems, but those of skill in the art will recognize that the assembly10 is analogous to a wide range of assemblies having two or more pulleysand belts of various types extending between the pulleys. An exampleassembly would include an electric motor having a first pulley and amachine having a second pulley and a belt providing power from theelectric motor to the machine.

Generally, to determine whether the tension in the belt is appropriate,the belt is deflected by a predetermined amount and the force requiredto achieve this deflection is compared to a specification for the beltor assembly. The displacement used may be based on the span between thepulleys. Typically, the displacement is 1/64^(th) inch per inch of span.For example, in a system where the span is 50 inches, the specificationmay indicate that a predetermined displacement of 50/64^(ths) of an inch(slightly more than three quarters of an inch) is used and theassociated force is 10 pounds. If the belt is displaced by ¾″ and theforce is less than 10 pounds, the belt tension is too low. If the forceis greater than 10 pounds, the tension is too high. As will be clear tothose of skill in the art, this is a form of measuring belt tension,even if a tension force along the belt is not actually measured orcalculated. As used herein, the term “measuring belt tension” may takethe form of determining the displacement and force and determining ifthe force matches, exceeds, or is below a specified level. Those ofskill in this art will understand how to determine belt span. Generally,the span is the distance between the tops of the pulleys, with top beingdefined relative to the plane of the belt.

As will also be clear to those of skill in the art, the belt tensioncould be measured (i.e. determined to be correct, high or low) byapplying a predetermined force and measuring the displacement. If thedisplacement is too large for the specified force, the tension is low;if the displacement is too small, the tension is high.

In FIGS. 1 and 2, the reference indicator takes the form of a firstlaser alignment element 20 and a second laser alignment element 22. Thelaser alignment elements may also be used for pulley alignment asdescribed in the inventor's issued U.S. Pat. No. 9,285,215, the entirecontents of which is incorporated herein by reference. The laseralignment elements are referred to as laser alignment tools in theearlier patent.

The second laser alignment element 22 is shown in more detail in FIG. 3and will be further described. Each of the laser alignment elements maytake this form, or may take other forms providing similar functionality.Laser alignment element 22 is provided with a housing 24 defined by anarcuate front surface 26 and an opposed rear surface 28, both of whichextend between a top surface 30 and a bottom surface 32. A first sidesurface 34 and an opposed second side surface 36 each extend between thefront 26, rear 28, top 30 and bottom 32 surfaces. In some versions, thetop and bottom surfaces are parallel to each other and the arcuate frontsurface 26 and rear surface 28 are both perpendicular to the top andbottom surfaces. As such, portions of the front surface 26 and rearsurface 28 may be parallel to each other. The arcuate front surface 26may be said to have a top end 38 adjacent the top surface 30 and abottom end 40 adjacent the bottom surface 32. A central region 42 isdefined between the top end 38 and bottom end 40 and an aperture 44 isdisposed in the central region 42. In the illustrated embodiment, thearcuate front face 26 is smoothly curved between the two sides 34 and 36with the central region 42 projecting slightly from the curved surface.The curved surface may be of a constant radius or arc or may be curvedin other ways. The term “arcuate” should be interpreted to mean a curvedsurface and is not limited to a constant arc. Further, the curvedsurface is curved from the side 34 to the side 36, not from the topsurface 30 to the bottom surface 32. Most or all of the front surface 26is preferably flat from the top surface 30 to the bottom surface 32 andperpendicular to these surfaces. As shown, the front surface is curvedoutwardly, so may be considered a convexly arcuate front surface.

As will be described in more detail below, a laser light source isdisposed in the body of laser alignment element 22 and configured toproject a sheet or plane of laser light from the aperture 44. When twolaser alignment elements are used as shown in FIGS. 1 and 2, the sheetof laser light from the second laser alignment element 22 illuminatesthe arcuate front surface of the first laser alignment element 20 andthe sheet of laser light from the first laser alignment element 20illuminates the arcuate front surface 26 of the second laser alignmentelement 22.

Referring again to FIG. 3, the arcuate front surface 26 is furtherprovided with a target pattern 46 disposed thereon. In some embodiments,target pattern 46 is a plurality of lines 48 disposed parallel to oneanother running lengthwise along the arcuate front surface 26. Theplurality of lines 48 may comprise a plurality of patterned color schemealignment strips extending parallel with the elongated axis of thearcuate front surface 26. A central one of the lines 48 of the targetpattern 46 may be white to clearly display a laser line when illuminatedby the sheet of laser light of the other laser alignment element. Whentwo laser alignment elements are coplanar with each other, the sheet oflaser light from each will illuminate the central line of the targetpattern of the other laser alignment element. If the two laser alignmentelements are not coplanar, the position of the sheet of light on eachfront surface may be referenced to allow adjustment until the elementsare coplanar.

In order to support the laser alignment elements 20 and 22 in a positionto define the reference position, they may be attached to the pulleys 12and 14, respectively, as shown in FIGS. 1 and 2. In an embodiment, thereference indicator may further include, in addition to the laseralignment elements 20 and 22, support brackets and support plates. FIGS.1 and 2 illustrate the first laser alignment element 20 being supportedby support bracket 50 and support plate 54 and second laser alignmentelement 22 supported by support bracket 52 and support plate 56. Thesupport bracket 52 and support plate 56 will be described in more detailwith reference to FIG. 3.

FIG. 3 shows the second laser alignment element 22, the support bracket52, and the support plate 56 separated for clarity, along with a portionof pulley 14 in phantom line. The bracket 52 is a right-angle brackethaving a first surface 58 attachable to a face 60 of the pulley 14 and asecond surface 62 at a right angle to the first surface 58. The lowerpart (in the illustrated orientation) includes the first surface 58 andhas a plurality of magnets 64 for magnetically attaching the firstsurface to the face 60 of the pulley 14. The upper part includes thesecond surface 62 and also includes a plurality of magnets 66. The laseralignment element 22 may have its own magnets for magnetically attachingto a surface and/or may be supported on the second surface 62, therebypositioning the laser alignment element 22 in a plane perpendicular tothe face 60 of the pulley 14. However, the support plate 56 may also beused, to provide more flexibility in positioning the laser alignmentelement 22 and providing a larger support surface. As shown, the supportplate 56 is a planar element, typically formed of ferromagneticmaterial, with a lower surface 70 and an opposed parallel upper surface72. The support plate 56 is magnetically attached to the second surface62 of the bracket 52 and the laser alignment element may be magneticallyattached to the upper surface 72 of the support plate 56.

In use, the support brackets 50 and 52 are magnetically attached to thefaces of the pulleys 12 and 14, respectively, the support plates 54 and56 are magnetically attached to the brackets 50 and 52, respectively,and the laser alignment elements 20 and 22 are magnetically attached tosupport plates 54 and 56, respectively. The positions are then adjusteduntil the laser alignment elements 20 and 22 are coplanar. The coplanarlaser sheets projected by the laser alignment elements 20 and 22 thencooperate to define a reference laser sheet or line, which defines thereference position for practicing an embodiment of the presentinvention. The reference laser sheet is typically a short distance abovethe upper surface of the belt and generally parallel thereto, though itis not required that the laser sheet be parallel to the belt surface aslong as the laser sheet provides a reference position relative to theupper surface to allow displacement measurements. It is noted that thesesteps are typically performed after aligning the pulleys in accordancewith the inventor's earlier patent.

FIG. 2 shows a force measurement device 80 with a probe element 82attached thereto. The probe element is a generally elongated elementhaving a distal 84 end that is positioned on the upper surface 86 of thebelt 16 to apply a force to the upper surface, preferably generallyperpendicularly to the upper surface 86 so as to deflect the beltdownwardly (in the illustrated orientation) to determine belt tension. Aproximal end 88 of the probe element is attached to the remainder of theforce measurement device. The probe element may form part of the forcemeasurement device, be integral therewith, or be detachable therefrom.The force measurement device 80 may take a variety of forms, with theillustrated embodiment including a display operable to show the forcebeing exerted through the probe element onto the upper surface of thebelt. The laser light from the laser alignment elements 20 and 22 isrepresented by a dashed line 90; the light illuminates the sides of theprobe element 82 so that movement of the probe element relative to thelight can be observed. The combination of the force measurement deviceand the probe element may be referred to as a force/probe assembly. Thisassembly may be an integrated probe and force measurement device withthe measurement markings thereon. As an example, the assembly could looklike an elongated probe with the force measurement functionality builtinto the probe itself.

In FIGS. 1 and 2, the belt 16 is a single belt, to represent thesimplest use of the present invention. However, the invention may alsobe used with more complex systems including, but not limited to, bandedbelts such as the belt 92 in FIG. 4. Such a belt comprises a pluralityof V-belts that are banded together by a top element. Belt tension ischecked in a manner similar to a single V-belt except that more force istypically required and it is helpful to spread this force over the spanof the banded belt. For this purpose, a bar 94 may be provided forspreading the load from the probe element 82 over the entire belt. Inthe illustrated embodiment, the bar 94 has a recess at a midpoint forreceiving the distal end 84 of the probe element 82.

FIG. 4 will be referred to for further details of an embodiment of theprobe element 82. In this embodiment, the probe element 82 has athreaded shaft 96 extending from the distal end 84 to the proximal end88 and a measurement element 98 that is received onto the shaft and maybe adjusted upwardly and downwardly. In this example, the measurementelement 98 is square in cross-section so as to have 4 side surfaces. Themeasurement element 98 has a first set of measurement markings 100 onone of the sides and a second set of measurement markings 102 on anotherof the sides. In this example, the first set of markings 100 aredisplacement markings in inches while the second set of measurementmarkings are indications of span in centimeters. Additional sides mayprovide displacement markings in metric units and span in inches. Incertain uses of the present invention, the span between the pulleysdetermines the predetermined displacement required for checking belttension. That is, for a belt having a given span, a correspondingdisplacement is always used and the force is provided by aspecification. In the illustrated example, a user may determine thedisplacement required by reference to the span markings. An adjustableindicator 104 is provided on the measurement element 98 and may be movedupwardly or downwardly to indicate a position to be used in the methodof the present invention. In FIG. 4, the indicator 104 is positioned atapproximately 1 inch of displacement, corresponding to a little morethan 150 centimeters of span. Typically, the displacement is 1/64^(th)inch per inch of span. In the illustrated example, 150 centimeters ofspan is approximately 59 inches, so the displacement is 59/64^(th) of aninch. In one example, the indicator is a rubber ring that may be slid orrolled upwardly and downwardly on the measurement element 98, but theindicator may take a variety of forms. In the illustrated embodiment,the distal end 84 of the probe element may has a collar 85 to preventthe measurement element from being threaded off the end of the threadedshaft. The lower end of the measurement element may have a recess toallow the collar 85 to be received into the body of the measurementelement such that the lower end is close to the distal end 84 forcertain measurements.

In the illustrated embodiment, the lower end 106 the measurement element98 is a zero location for the displacement markings 100. In use, thedistal end 84 of the probe element 82 is positioned on the upper surface86 of the belt, generally perpendicularly thereto and at a midpoint ofthe span, as shown in FIG. 2. With the distal end 84 just touching thebelt, but not displacing the belt, the measurement element 98 is rotatedon the shaft 96 until the lower end 106 is at the reference positiondefined by the light 90. With the indicator 104 set to the predetermineddisplacement, a force is applied generally perpendicularly to the uppersurface 86 of the belt, using the probe element. The force is increaseduntil the displacement reaches the predetermined displacement, asindicated by the indicator 104. That is, as the belt is displaced, thelight 90 will illuminate the displacement markings 100 allowing a userto determine when the predetermined displacement has been reached. Theforce, as determined by the force measurement device 80, is then read orrecorded. In some examples, the force measurement device will record themaximum force applied.

As mentioned previously, it would be possible to check tension byapplying a predetermined force and then checking the displacement. Theforce measurement device 80 may be set to beep or provide other types ofindication when a predetermined force is reached and the user may thenobserve the corresponding displacement.

A variety of alternatives are also available. In one embodiment, theindicator 104 includes a light sensor operable to determine when thelight 90 illuminates the indicator. The indicator may then provide anaudible alert or may communication wirelessly or through a wiredconnection, either to an external device or to the force measurementdevice, allowing a tension check without directly observing the light 90on the measurement markings 100. In a further embodiment, the probeelement may have a sensor operable to sense a position along the probethat is being illuminated, so as to determine displacement along thelength. Such a sensor could take the form of a plurality of discretesensors or a continuous sensor. Again, the sensor may provide an alertor communicate with an external device or the force measurement device.As yet another embodiment, a sensor may be provided for reading themeasurement markings on the probe element to allow the sensor todetermine the displacement. The measurement markings may includemachine-readable markings that are read by a video sensor, therebydetermining the position of the light on the markings. Such a sensor maybe integrated into one or more of the laser alignment devices fordirectly determining displacement.

As mentioned previously, the invention may be practiced with a singlelaser alignment element, 20 or 22, as long as it provides a referenceposition on the probe. Further, other types of reference indicators maybe used, though a laser light source is preferred. As examples, thereference indicator may be a straight edge extending between thepulleys, may be an adjacent belt (where the upper surface of theadjacent belt defines the reference position) or other approaches may beused.

Terms such as “generally parallel” and “generally perpendicular” havebeen used herein. As used herein, the term “generally” should beinterpreted as sufficiently close to allow the invention to bepracticed. For example, as will be clear to those of skill in the art,it is desirable to apply the displacement force to the belt in adirection perpendicular to the surface of the belt. However, it is notnecessary that the force be applied absolutely perpendicularly in orderto obtain a reliable indication of belt tension. As such, “generallyperpendicular” should be interpreted as being close enough toperpendicular to provide results that are acceptable within theindustry. While being within a few degrees of perpendicular is idea,errors of five or even ten degrees or more degrees may not causeunacceptable errors in tension checking. Further, while it is desirableto apply the force at the center of the span, the term “midpoint” hasbeen used herein to indicate a location near enough to the center toprovide acceptable results.

As will be clear to those of skill in the art, the herein describedembodiments of the present invention may be altered in various wayswithout departing from the scope or teaching of this disclosure. Assuch, this disclosure should be interpreted broadly. The followingclaims define the scope of some embodiments.

The invention claimed is:
 1. A method of checking belt tension of a beltextending between two or more pulleys, the belt having an upper surfaceand a span between the pulleys, the method comprising the steps of:providing a reference indicator defining a reference position relativeto the upper surface of the belt in an undeflected state; providing aforce/probe assembly operable to measure a force and having measurementmarkings disposed thereon, the force/probe assembly having a distal endand being configured to measure a force applied to the distal end;positioning the distal end of the force/probe assembly on the uppersurface of the belt at a midpoint of the span; applying a forcegenerally perpendicular to the upper surface of the belt using theforce/probe assembly; either: deflecting the belt a predetermineddistance, as determined by a change in position of the measurementmarkings relative to the reference indicator, and measuring the forceapplied generally perpendicularly to the outer surface using theforce/probe assembly; or deflecting the belt using the force/probeassembly until the force applied generally perpendicularly to the uppersurface is equal to a predetermined force, and measuring the deflectionof the belt, as determined by a change in position of the measurementmarkings relative to the reference indicator; and determining the belttension based on the force and distance during the deflecting step;wherein: the step of providing the reference indicator comprises:providing a first laser alignment element operable to project laserlight in a plane; positioning the first laser alignment element suchthat the laser light in the plane is projected generally parallel to theupper surface of the belt in the undeflected state; and wherein thechange in position of the measurement markings relative to the referenceindicator comprises the change in position of the measurement markingsrelative to the projected laser light.
 2. The method according to claim1, wherein the force/probe assembly comprises: a force measurementdevice operable to measure a force; and a probe element having themeasurement markings disposed thereon, the probe element having an enddefining the distal end of the force/probe assembly, the probe elementbeing connected with the force measurement device such that a forceapplied to the end of the probe element is measured by the forcemeasurement device.
 3. The method according to claim 2, wherein: alinear position of the measurement markings of the probe element areadjustable relative to the distal end of the force/probe assembly; andthe method further comprises, after the positioning step and before theapplying step, adjusting the linear position of the measurement markingsrelative to the distal end until the reference indicator is aligned witha zero location of the measurement markings.
 4. The method according toclaim 3, wherein the probe element has a shaft and a measurement elementmovably received on the shaft, the measurement element having themeasurement markings disposed thereon.
 5. The method according to claim4, wherein the zero location of the measurement markings is an end ofthe measurement element.
 6. The method according to claim 2, wherein:the probe element has an indicator movable relative to the measurementmarkings; and the method further comprises positioning the indicator ata predetermined position prior to the applying step, the positioncorresponding to the predetermined deflection of the belt.
 7. The methodaccording to claim 2, wherein: the probe element has a proximal endconnected to the force measurement device and the proximal end isseparable from the force measurement device; and the method furtherincludes disposing the proximal end of the probe element on the forcemeasurement device such that a force applied to the end of the probeelement is measured by the force measurement device.
 8. The methodaccording to claim 1, wherein: the step of providing the referenceindicator further comprises: providing a second laser alignment elementoperable to project laser light in a plane; and positioning the secondlaser alignment element such that the laser light projected by thesecond laser alignment element is generally in the same plane as thelaser light from the first laser alignment element.
 9. The methodaccording to claim 8, wherein: the steps of positioning the first andsecond laser alignment elements comprises attaching the alignmentelements to respective ones of the two or more pulleys such that thealignment elements project light towards each other.
 10. The methodaccording to claim 9, further comprising: providing a first and secondsupport bracket; and the step of attaching the alignment elements to therespective pulleys comprises attaching a respective one of the supportbrackets to each pulley and attaching each alignment element to therespective support bracket.
 11. The method according to claim 10,wherein the first and second support brackets are right-angle bracketseach having a first surface attachable to a face of a pulley and asecond surface at a right angle to the first surface, the second surfaceof each support bracket supporting a respective one of the alignmentelements.
 12. The method according to claim 10, wherein the supportbrackets each have magnets for magnetically attaching to the face of therespective pulley.
 13. The method according to claim 1, wherein themeasurement markings of the force/probe assembly include displacementmarkings and span markings corresponding to the displacement markings,the displacement marking associated with each span marking indicating adisplacement to be used for the respective span indicated by the spanmarking.
 14. The method according to claim 2, wherein a distance betweenthe force measurement device and the distal end of the probe elementdoes not change during the force applying step.